No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Improved cosmological constraints from a joint analysis of the SDSS-II and SNLS supernova samples
Abstract
Aims. We present cosmological constraints from a joint analysis of type Ia supernova (SN Ia) observations obtained by the SDSS-II and SNLS collaborations. The dataset includes several low-redshift samples (z< 0.1), all three seasons from the SDSS-II (0.05 <z< 0.4), and three years from SNLS (0.2 <z< 1), and it totals 740 spectroscopically confirmed type Ia supernovae with high-quality light curves.
Methods. We followed the methods and assumptions of the SNLS three-year data analysis except for the following important improvements: 1) the addition of the full SDSS-II spectroscopically-confirmed SN Ia sample in both the training of the SALT2 light-curve model and in the Hubble diagram analysis (374 SNe); 2) intercalibration of the SNLS and SDSS surveys and reduced systematic uncertainties in the photometric calibration, performed blindly with respect to the cosmology analysis; and 3) a thorough investigation of systematic errors associated with the SALT2 modeling of SN Ia light curves.
Results. We produce recalibrated SN Ia light curves and associated distances for the SDSS-II and SNLS samples. The large SDSS-II sample provides an effective, independent, low-z anchor for the Hubble diagram and reduces the systematic error from calibration systematics in the low-z SN sample. For a flat ΛCDM cosmology, we find Ωm =0.295 ± 0.034 (stat+sys), a value consistent with the most recent cosmic microwave background (CMB) measurement from the Planck and WMAP experiments. Our result is 1.8σ (stat+sys) different than the previously published result of SNLS three-year data. The change is due primarily to improvements in the SNLS photometric calibration. When combined with CMB constraints, we measure a constant dark-energy equation of state parameter w =−1.018 ± 0.057 (stat+sys) for a flat universe. Adding baryon acoustic oscillation distance measurements gives similar constraints: w =−1.027 ± 0.055. Our supernova measurements provide the most stringent constraints to date on the nature of dark energy.
... The aim of this paper, which is partially motivated by [11], is to consider simple departures from the FLRW limit, modifying just one of these functions and to study, to a large part analytically, the resulting dynamics. This will not necessarily lead to competitive realistic models although we shall use observational data from supernovae of type Ia (SNIa) to fix our model parameters [12]. We consider our models to be simple test models which serve to illustrate basic properties of the LTB solution. ...
... Now we explain, how the already used best-fit values for t B0 and r c were obtained. We have used the Joint Light-curve Analysis sample [12] that consist of several low-redshift samples (z < 0.1), the SDSS-II (0.05 < z < 0.4), SNLS (0.2 < z < 1) and the HST (z > 1). This extended sample of 740 spectroscopically confirmed type Ia supernovae with high quality light curves is know as the JLA sample. ...
... This extended sample of 740 spectroscopically confirmed type Ia supernovae with high quality light curves is know as the JLA sample. Following [12], the observational distance modulus is ...
Based on the Lema\^itre-Tolman-Bondi (LTB) metric we consider two flat inhomogeneous big-bang models. We aim at clarifying, as far as possible analytically, basic features of the dynamics of the simplest inhomogeneous models and to point out the potential usefulness of exact inhomogeneous solutions as generalizations of the homogeneous configurations of the cosmological standard model. We discuss explicitly partial successes but also potential pitfalls of these simplest models. Although primarily seen as toy models, the relevant free parameters are fixed by best-fit values using the Joint Light-curve Analysis (JLA)-sample data. On the basis of a likelihood analysis we find that a local hump with an extension of almost 2 Gpc provides a better description of the observations than a local void for which we obtain a best-fit scale of about 30 Mpc. Future redshift-drift measurements are discussed as a promising tool to discriminate between inhomogeneous configurations and the CDM model.
... We shall consider the cosmic substratum as built of this dark sector together with baryons and radiation. Starting point of the numerical part is a confrontation of the background dynamics with the JLA sample of supernovae of type Ia [33]. The parameter α which represents a measure of the distance to the ΛCDM model is poorly constrained by the SNIa data. ...
... respectively. In the following section we confront this background dynamics with the binned SNIa data from the JLA sample [33]. Since even the most distant supernovae have a low redshift (compared with the redshift of the last-scattering surface), the radiation component in the energy balance is small and the approximate solution is justified for this analysis. ...
... where the observational distance modulus µ obs has the structure [33] ...
Yes, but only for a parameter value that makes it almost coincide with the standard model. We reconsider the cosmological dynamics of a generalized Chaplygin gas (gCg) which is split into a cold dark matter (CDM) part and a dark energy (DE) component with constant equation of state. This model, which implies a specific interaction between CDM and DE, has a CDM limit and provides the basis for studying deviations from the latter. Including matter and radiation, we use the (modified) CLASS code \cite{class} to construct the CMB and matter power spectra in order to search for a gCg-based concordance model that is in agreement with the SNIa data from the JLA sample and with recent Planck data. The results reveal that the gCg parameter is restricted to , i.e., to values very close to the CDM limit . This excludes, in particular, models in which DE decays linearly with the Hubble rate.
... While the well-known "fine tuning" problem with Λ [8][9][10][11][12] prompts one to look into the theoretical aspects of a dynamical DE, observations generally favour the ΛCDM model (with Λ and the cold dark matter (CDM) as the dominant energy contributors in the universe) [13][14][15][16]. Nevertheless, the type Ia supernovae data [17][18][19], as well as the WMAP [20,21] and PLANCK results [22,23], do provide some room for a DE with at least a slowly time-varying equation of state (EoS) parameter w X , on an average close to the ΛCDM value (equal to −1). ...
... This is of course the action of a scalar-tensor theory in the original Jordan frame [67,68], which is characterized by a running gravitational coupling parameter 19) defined so that at the present epoch t = t 0 , we have G eff (t 0 ) = G under the stipulation ...
... Dataset 4: PLANCK 2015 CMB power spectra (TT, TE, EE) and LowP, combined with weak lensing data (Lensing) [241] and external data (Ext) that includes the BAO and H 0 priors and the Joint Lightcurve Analysis (JLA) sample [19] constructed from the SNLS [240] and the Sloan Digital Sky Survey (SDSS) [242,243] data, and many low redshift type-1a supernovae samples. ...
We study the dynamical aspects of dark energy in the context of a non-minimally coupled scalar field with curvature and torsion. Whereas the scalar field acts as the source of the trace mode of torsion, a suitable constraint on the torsion pseudo-trace provides a mass term for the scalar field in the effective action. In the equivalent scalar-tensor framework, we find explicit cosmological solutions representing dark energy in both Einstein and Jordan frames. We demand the dynamical evolution of the dark energy to be weak enough, so that the present-day values of the cosmological parameters could be estimated keeping them within the confidence limits set for the standard \LCDM model from recent observations. For such estimates, we examine the variations of the effective matter density and the dark energy equation of state parameters over different redshift ranges. In spite of being weakly dynamic, the dark energy component differs significantly from the cosmological constant, both in characteristics and features, for e.g. it interacts with the cosmological (dust) fluid in the Einstein frame, and crosses the phantom barrier in the Jordan frame. We also obtain the upper bounds on the torsion mode parameters and the lower bound on the effective Brans-Dicke parameter. The latter turns out to be fairly large, and in agreement with the local gravity constraints, which therefore come in support of our analysis.
... Additionally, when the SDSS-II/SNLS-3 Joint Lightcurve Analysis (JLA) catalogue of SNe Ia [15] was analysed in the heliocentric frame (after removing demonstrably incorrect peculiar velocity corrections), the inferred acceleration of the expansion was found to be anisotropic, with the dipole component of the deceleration parameter q 0 dominating over its monopole component out to redshift z ∼ 0.1 [16]. Acceleration due to Λ must be isotropic, so this rejects the ΛCDM model, at 3.9σ. ...
... not multiple observations of the same supernova). Of the 740 SNe Ia which made up the JLA sample [15], 584 were included in Pantheon+ after quality cuts. Of the additional 949 SNe Ia, 446 have been added at redshift z < 0.1 as seen in Fig. 2; of these, 66 are below the lowest redshift (z = 0.00937) in the JLA catalogue. ...
... Refs. [15,24,25]) in using the 'constrained χ 2 ' statistic in which error bars are adjusted until a good fit with χ 2 /d.o.f=1 is obtained. This is however quite unsuitable for goodness-of-fit testing or model selection [26]. ...
We employ Maximum Likelihood Estimators to examine the Pantheon+ catalogue of Type Ia supernovae for large scale anisotropies in the expansion rate of the Universe. The analyses are carried out in the heliocentric frame, the CMB frame, as well as the Local Group frame. In all frames, the Hubble expansion rate in the redshift range 0.023 < z < 0.15 is found to have a statistically significant dipolar variation exceeding 1.5 km/s/Mpc, i.e. bigger than the claimed 1% uncertainty in the SH0ES measurement of the Hubble parameter H_0. The deceleration parameter too has a redshift-dependent dipolar modulation at >5 sigma significance, consistent with previous findings using the SDSSII/SNLS3 Joint Lightcurve Analysis catalogue. The inferred cosmic acceleration cannot therefore be due to a Cosmological Constant, but is probably an apparent (general relativistic) effect due to the anomalous bulk flow in our local Universe.
... The discovery of the accelerated expansion of our Universe using Supernova Ia observations revolutionized our understanding of modern cosmology [1][2][3][4][5][6]. The standard model of cosmology, CDM, is composed of ordinary matter, a dark energy modeled as a cosmological constant that is responsible for the acceleration of the Universe, and Cold Dark Matter (CDM) [7] that shapes the cosmic structure through gravitational influence. ...
... Over the last two decades, numerous studies have utilized Type Ia Supernovae (SNIa) as the primary probe for investigating dark energy [4,[74][75][76]. Through successive SNIa programs, our precision in understanding dark energy has significantly improved, with efforts still ongoing [77][78][79]. ...
... mented canonical genetic algorithms with elitism from the DEAP library [115,116] (for details on genetic algorithms we recommend Ref. [49]). In our case, we consolidated the search space with the number of layers ∈ [3,4], the number of neurons for hidden layers ∈ [100,200], and batch size ∈ [8,16,32,64]. ...
In this paper, we present an analysis of Supernova Ia (SNIa) distance moduli and dark energy using an Artificial Neural Network (ANN) reconstruction based on LSST simulated three-year SNIa data. The ANNs employed in this study utilize genetic algorithms for hyperparameter tuning and Monte Carlo Dropout for predictions. Our ANN reconstruction architecture is capable of modeling both the distance moduli and their associated statistical errors given redshift values. We compare the performance of the ANN-based reconstruction with two theoretical dark energy models: LCDM and Chevallier-Linder-Polarski (CPL). Bayesian analysis is conducted for these theoretical models using the LSST simulations and compared with observations from Pantheon and Pantheon+ SNIa real data. We demonstrate that our model-independent ANN reconstruction is consistent with both theoretical models. Performance metrics and statistical tests reveal that the ANN produces distance modulus estimates that align well with the LSST dataset and exhibit only minor discrepancies with LCDM and CPL.
... The discovery of the accelerated expansion of our Universe using Supernova Ia observations revolutionized our understanding of modern cosmology [1][2][3][4][5][6]. The standard model of cosmology, ΛCDM, is composed of ordinary matter, a dark energy modeled as a cosmological constant Λ that is responsible for the acceleration of the Universe, and Cold Dark Matter (CDM) [7] that shapes the cosmic structure through gravitational influence. ...
... therefore SNIa provides a direct and robust method to probe dark energy. Over the last two decades, numerous studies have utilized Type Ia Supernovae (SNIa) as the primary probe for investigating dark energy [4,[55][56][57]. Through successive SNIa programs, our precision in understanding dark energy has significantly improved, with efforts still ongoing [58][59][60]. ...
... • To find a proper combination of hyperparameters, we set the search space for the use of nnogada [30] and their implemented simple genetic algorithms with elitism from the DEAP library [99,100] (for details on genetic algorithms we recommend Ref. [32]). In our case, we consolidated the search space with the number of layers ∈ [3,4], the number of neurons for hidden layers ∈ [100,200], and batch size ∈ [8,16,32,64]. ...
... SNe Ia provided the first signal for a universe acceleration [83,84], and they serve as the main observational data set to probe the late-time, dark-energy epoch. In this work we consider the latest "joint light curves" (JLA) sample [85] containing 740 SNe Ia in the redshift range z ∈ [0.01, 1.30]. From the observational point of view, the distance modulus of a SNe Ia can be abstracted from its light curve, assuming that supernovae with identical color, shape and galactic environment, have on average the same intrinsic luminosity for all redshifts. ...
... In particular, we used the recent cosmic chronometer data set, along with the latest measured value of the local Hubble parameter, H 0 = 73.02 ± 1.79 km s −1 Mpc −1 [82], while we additionally performed a combined analysis using the latest "joint light curves" (JLA) SNe Ia sample [85] in the redshift range z ∈ [0.01, 1.30], as well as baryon acoustic oscillation (BAO) data points from various probes. ...
We use the recently released cosmic chronometer data and the latest measured value of the local Hubble parameter, combined with the latest joint light curves of Supernovae Type Ia, and Baryon Acoustic Oscillation distance measurements, in order to impose constraints on the viable and most used f(R) gravity models. We consider four f(R) models, namely the Hu-Sawicki, the Starobinsky, the Tsujikawa, and the exponential one, and we parametrize them introducing a distortion parameter b that quantifies the deviation from CDM cosmology. Our analysis reveals that a small but non-zero deviation from CDM cosmology is slightly favored, with the corresponding fittings exhibiting very efficient AIC and BIC Information Criteria values. Clearly, f(R) gravity is consistent with observations, and it can serve as a candidate for modified gravity.
... On the other hand, from type Ia supernovae (SNe Ia) samples larger densities are obtained. For example, the JLA compilation furnishes Ω m0 ≈ 0.3 [38] or even Ω m0 ≈ 0.4, depending on the light-curve calibration method used [39]. Larger values are also derived from CMB observations [1]. ...
... In our analysis, we use the Joint Light-curve Analysis (JLA) supernovae data [38] together with the second release of Planck data [64] (hereafter TT+lowP), namely the high-Planck temperature data (in the range of 30 < < 2508) from the 100-, 143-, and 217-GHz halfmission TT cross-spectra, and the low-P data by the joint TT, EE, BB and TE likelihood (in the range of 2 < < 29). It is worth mentioning that, compared to other recent SNe Ia compilations e.g. the Pantheon compilation [65], the JLA sample has the advantage of allowing the light-curve recalibration with the model under consideration, which is an important issue when testing alternative cosmologies. ...
We study observational signatures of non-gravitational interactions between the dark components of the cosmic fluid, which can be either due to creation of dark particles from the expanding vacuum or an effect of the clustering of a dynamical dark energy. In particular, we analyse a class of interacting models ((t)CDM), characterised by the parameter , that behaves at background level like cold matter at early times and tends to a cosmological constant in the asymptotic future. In our analysis we consider both background and primordial perturbations evolutions of the model. We use Cosmic Microwave Background (CMB) data together with late time observations, such as the Joint Light-curve Analysis (JLA) supernovae data, the Hubble Space Telescope (HST) measurement of the local value of the Hubble-Lema\^itre parameter, and primordial deuterium abundance from Ly systems to test the observational viability of the model and some of its extensions. We found that there is no preference for values of different from zero (characterising interaction), even if there are some indications for positive values when the minimal (t)CDM model is analysed. When extra degrees of freedom in the relativistic component of the cosmic fluid are considered, the data favour negative values of , which means an energy flux from dark energy to dark matter.
... The formalism described above can be used now to test the scaling cosmology model against the observational data. The main motivation of this chapter is to compare the parameter selection obtained by background tests using SNe Ia data from the JLA sample [47] and baryon acoustic oscillations (BAO) data from 6dFGS [48], SDSS [49], BOSS CMASS [50] and the WiggleZ survey [51], with a perturbative test using the CMB power spectrum data from Planck [52]. In the simplified analysis of this paper we focus on the impact of variations of the parameter ξ on the spectrum. ...
... where ∆y(θ) = y i − y(x i ; θ) and θ are the free parameters. The y(x i |θ) represent the theoretical predictions for a given set of parameters and C is the covariance matrix that in the case of JLA is given in [47]. In the case of the BAO analysis, 6dFGS, SDSS and BOSS CMASS data are mutually uncorrelated and they are also not correlated with WiggleZ data. ...
An interaction between dark matter and dark energy, proportional to the product of their energy densities, results in a scaling behavior of the ratio of these densities with respect to the scale factor of the Robertson-Walker metric. This gives rise to a class of cosmological models which deviate from the standard model in an analytically tractable way. In particular, it becomes possible to quantify the role of potential dark-energy perturbations. We investigate the impact of this interaction on the structure formation process. Using the (modified) CAMB code we obtain the CMB spectrum as well as the linear matter power spectrum. It is shown that the strong degeneracy in the parameter space present in the background analysis is considerably reduced by considering \textit{Planck} data. Our analysis is compatible with the CDM model at the confidence level with a slightly preferred direction of the energy flow from dark matter to dark energy.
... 1 While the question as to how the DE evolves has been contemplated by a plethora of theoretical surmises and conjectures, [2][3][4] observations have mostly been in favour of a non-dynamical DE, reminiscent of a cosmological constant Λ, at low to moderately high redshifts. [5][6][7] However, some scope is there to look for (albeit mild) deviations from the concordant ΛCDM model, comprising of Λ and cold dark matter (CDM) as the dominant constituents of the universe. [8][9][10] In fact, the dynamical aspects of the DE are always worth examining, for a sufficiently longer span of evolution, tracing back from deep in the past, till extrapolating to high blueshifts in the future. ...
... which is roughly the observational prediction[5][6][7] for most of the model-independent and model-dependent DE parametrizations), and (ii) β = 0.01 (which is the order of magnitude estimation 50 for the above ansatz, using the WMAP and Planck results 5a) shows the evolution of the density parameters Ω(m) eff (N ) and Ω X (N ) over the fiducial trajectory (with the above initial conditions) for a fairly wide range of e-foldings N ∈ {−5, 5} h . As expected (in view of the small value of β), Evolution of (a) the density parameters Ω(m) eff and ΩX, and (b) EoS parameters w X and w, over the trajectory with initial conditions [X(0) = 0.0082, Y (0) = 0.8327] for β = 0 ...
We study the phase space dynamics of cosmological models in the theoretical formulations of non-minimal metric-torsion couplings with a scalar field, and investigate in particular the critical points which yield stable solutions exhibiting cosmic acceleration driven by the {\em dark energy}. The latter is defined in a way that it effectively has no direct interaction with the cosmological fluid, although in an equivalent scalar-tensor cosmological setup the scalar field interacts with the fluid (which we consider to be the pressureless dust). Determining the conditions for the existence of the stable critical points we check their physical viability, in both Einstein and Jordan frames. We also verify that in either of these frames, the evolution of the universe at the corresponding stable points matches with that given by the respective exact solutions we have found in an earlier work (arXiv: 1611.00654 [gr-qc]). We not only examine the regions of physical relevance for the trajectories in the phase space when the coupling parameter is varied, but also demonstrate the evolution profiles of the cosmological parameters of interest along fiducial trajectories in the effectively non-interacting scenarios, in both Einstein and Jordan frames.
... It is interesting to note that in the galaxy simulation the effect of inhomogeneity on the Hubble diagram acts to bias the inferred amount of dark energy. That is, if we fit the data Figure 9: Dispersion of the Hubble diagram σ lens due to gravitational lensing in each of our two simulations, compared with the ansatz of the joint light-curve analysis [79]. from our galaxy simulation to a spatially flat ΛCDM model by minimizing the χ 2 statistic, ...
... Finally, let us close this section with a remark on the scatter of supernova data due to gravitational lensing in the joint light-curve analysis (JLA) [79]. The results of the JLA, which assume σ lens (z) = 0.055z, are shown in figure 9 together with our numerical results from ray tracing. ...
On small scales the observable Universe is highly inhomogeneous, with galaxies and clusters forming a complex web of voids and filaments. The optical properties of such configurations can be quite different from the perfectly smooth Friedmann-Lema\^itre-Robertson-Walker (FLRW) solutions that are frequently used in cosmology, and must be well understood if we are to make precise inferences about fundamental physics from cosmological observations. We investigate this problem by calculating redshifts and luminosity distances within a class of cosmological models that are constructed explicitly in order to allow for large density contrasts on small scales. Our study of optics is then achieved by propagating one hundred thousand null geodesics through such space-times, with matter arranged in either compact opaque objects or diffuse transparent haloes. We find that in the absence of opaque objects, the mean of our ray tracing results faithfully reproduces the expectations from FLRW cosmology. When opaque objects with sizes similar to those of galactic bulges are introduced, however, we find that the mean of distance measures can be shifted up from FLRW predictions by as much as . This bias is due to the viable photon trajectories being restricted by the presence of the opaque objects, which means that they cannot probe the regions of space-time with the highest curvature. It corresponds to a positive bias of order in the estimation of and highlights the important consequences that astronomical selection effects can have on cosmological observables.
... We use the JLA compilation of type Ia supernovae [62]. The JLA compilation is from a joint analysis of type Ia supernova observations in the redshift range of z ∈ [0.01, 1.30]. ...
... It consists of 740 Ia supernovae, which collects several low-redshift samples, obtained from three seasons from SDSS-II, three years from SNLS, and a few high-redshift samples from the HST. According to the observational point of view, we can get the distance modulus of a SN Ia from its light curve through the empirical linear relation [62], ...
We make a comparison for ten typical, popular dark energy models according to their capabilities of fitting the current observational data. The observational data we use in this work include the JLA sample of type Ia supernovae observation, the Planck 2015 distance priors of cosmic microwave background observation, the baryon acoustic oscillations measurements, and the direct measurement of the Hubble constant. Since the models have different numbers of parameters, in order to make a fair comparison, we employ the Akaike and Bayesian information criteria to assess the worth of the models. The analysis results show that, according to the capability of explaining observations, the cosmological constant model is still the best one among all the dark energy models. The generalized Chaplygin gas model, the constant w model, and the dark energy model are worse than the cosmological constant model, but still are good models compared to others. The holographic dark energy model, the new generalized Chaplygin gas model, and the Chevalliear-Polarski-Linder model can still fit the current observations well, but from an economically feasible perspective, they are not so good. The new agegraphic dark energy model, the Dvali-Gabadadze-Porrati model, and the Ricci dark energy model are excluded by the current observations.
... For the luminosity distance D L , we use the Joint Light Analysis (JLA) SNe Ia compilation [53]. It contains a set of 740 spectroscopically confirmed SNe Ia compiled by the SDSS-II supernova survey [54], SNLS survey [55] and a few from Hubble Space Telescope (HST) SNe observations [56] in the redshift region 0.01 < z < 1.3. ...
... However, in recent works it has been observed that α and β act like global parameters for a dataset across different cosmological models [57][58][59][60]. As α and β have little effect on our analysis, we will simply adopt the best fit values from Ref. [53] given as : α = 1.141 ± 0.006 and β = 3.101 ± 0.75. Once the distance modulus is known then by using the relation µ(z) = 5log 10 (D L (z)) + 25, [where D L is in Mpc] we can easily obtain the luminosity distance D L . ...
The construction of the cosmic distance-duality relation (CDDR) has been widely studied. However, its consistency with various new observables remains a topic of interest. We present a new way to constrain the CDDR using different dynamic and geometric properties of strong gravitational lenses (SGL) along with SNe Ia observations. We use a sample of 102 SGL with the measurement of corresponding velocity dispersion and Einstein radius . In addition, we also use a dataset of 12 two image lensing systems containing the measure of time delay between source images. Jointly these two datasets give us the angular diameter distance of the lens. Further, for luminosity distance, we use the 740 observations from JLA compilation of SNe Ia. To study the combined behavior of these datasets we use a model independent method, Gaussian Process (GP). We also check the efficiency of GP by applying it on simulated datasets, which are generated in a phenomenological way by using realistic cosmological error bars. Finally, we conclude that the combined bounds from the SGL and SNe Ia observation do not favor any deviation of CDDR and are in concordance with the standard value () within confidence region, which further strengthens the theoretical acceptance of CDDR.
... 1. Supernovae Type Ia: We include the latest Joint Light Curve analysis sample [47] from Supernovae Type Ia, one of the cosmological data sets to probe the nature of dark energy. The sample contains 740 number of Supernovae Type Ia data, distributed in the redshift interval z ∈ [0.01, 1.30]. ...
... whereμ is the vector of effective absolute magnitudes, C is the covariance metrix of µ quantifying the statistical and systematic errors (see [47] for details), andμ m (z) = 5 log 10 ...
We perform a detailed confrontation of various oscillating dark-energy parame-trizations with the latest sets of observational data. In particular, we use data from Joint Light Curve analysis (JLA) sample from Supernoave Type Ia, Baryon Acoustic Oscillations (BAO) distance measurements, Cosmic Microwave Background (CMB) observations, redshift space distortion, weak gravitational lensing, Hubble parameter measurements from cosmic chronometers, and we impose constraints on four oscillating models. From the analyses we find that the best-fit characters of almost all models are bent towards the phantom region, nevertheless in all of them the quintessential regime is also allowed within 1 confidence-level. Furthermore, the deviations from CDM cosmology are not significant, however for two of the models they could be visible at large scales, through the impact on the temperature anisotropy of the CMB spectra and on the matter power spectra. Finally, we peform the Bayesian analysis, which shows that the current observational data support the CDM paradigm over this set of oscillating dark-energy parametrizations.
... This leaves us with two possible choices: 1) a color-charged top-philic mediator denoted byt, which interacts with the right-handed top quark, and 2) a lepto-philic mediator τ , carrying only hypercharge while interacting with the right-handed τ -lepton. 37 An overview of the introduced dark sector particles is given in Table 6.1. ...
... It is agnostic to possible SM interactions of the matter in question, as it relies on the bending of light through massive objects within the LoS.4 Other important observations to constrain the cosmological abundances of certain energy components, on which we will not comment on further, come from supernovae measurements[37] and baryon acoustic oscillations[38]. ...
Dark matter stands out as one of the most important unsolved mysteries in particle physics and cosmology. We investigate the influence of non-perturbative effects on the production of dark matter as well as their impact on direct and indirect detection to attain insight on its fundamental nature. Specifically, we focus on Sommerfeld enhancement and the formation of dark matter bound states both of which can alter the total dark matter annihilation cross section and thus modify dark matter observables in the early and late Universe. To this end, we conducted two studies focusing on different dark matter observables, which are likely to be probed by upcoming experiments.
... Observational constraints play a pivotal role in testing and refining models of dynamic dark energy [9,10]. The reliability and validity of these models depend heavily on their consistency with a wide range of cosmological observations [11,12]. This paper will discuss how different observational techniques and data sets, from the Cosmic Microwave Background (CMB) to supernovae and galaxy clustering, provide stringent tests for these models [3,13]. ...
... Dynamic dark energy models can be tested and constrained by integrating them with observational data [11,12]. This integration involves comparing theoretical predictions with observed data, using statistical techniques to assess model viability [18,19]. ...
This paper is dedicated to examining dynamic dark energy models in the context of observational constraints and their implications for the universe's future. By integrating theoretical models with various observational data, we aim to provide a comprehensive view of how dynamic dark energy influences cosmic evolution and the universe's fate. This study tests these models against the latest observational evidence, including the Cosmic Microwave Background, supernovae, and large-scale structure surveys, to refine our understanding of the universe's accelerating expansion and the mysterious nature of dark energy.
... To fit this model, observations should be corrected for no time dilation as: μ(z) → μ(z) + 2.5 · lg(1 + z), where lg x ≡ log 10 x, and the distance modulus: μ(z) ≡ 5lgD L (z)(Mpc) + 25. In [13], I have used 31 binned points of the JLA compilation from Tables F.1 and F.2 of [14] (diagonal elements of the correlation matrix in Table F After non-forehead collisions, scattered photons should create the light-fromnowhere effect which has not an analog in the standard cosmological model. The ratio δ(z) of the scattered flux to the remainder reaching the observer is equal to [15]: ...
... The theoretical Hubble diagram μ 0 (z) of this model with b = 2.365 (solid); Supernovae 1a observational data (31 binned points of the JLA compilation) are taken from Tables F.1 and F.2 of[14] and corrected for no time dilation. ...
A brief review of the consequences of the hypothesis about the existence of a background of superstrong interacting gravitons is given. Gravity is seen as a shielding effect in a sea of low-energy gravitons, and Newton's constant can be calculated as a function of the background temperature. At very small distances, the phenomenon of asymptotic freedom arises. Restrictions on the geometric language and the ban on the existence of black holes are considered. Additional deceleration of massive bodies occurs due to forehead and backhead collisions with gravi-tons. Scattering of photons by background gravitons leads to a redshift of distant objects, their additional darkening and the appearance of a background of scattered photons. These effects could revolutionize cos-mology because they don't need dark energy, the Big Bang, etc. to explain observations.
... (a) For the model calculations, the cosmological parameters ΏM = 0.295, Ώλ = 0.705, w = −1.018 and h0 = 0.7 were used, based on 374 spectroscopically affirmed, upgraded SN1a supernovae from the most recent joint light-curve analysis (JLA) data index (Betoule et al. 2014). ...
... which is linear with distance, with an intercept on zero. Figure 1 shows the HD calculated with the parameters of the ΛCDM model, as set down by Betoule et al. (2014), in the RS range z = 0.01-1.35 for the log(z)/µ presentation. ...
Hubble diagrams are examined for SN1a supernovae in the redshift range z = 0.01–1.3 and for gamma ray bursts in the range z = 0.034–8.1. It is shown that in the low redshift range, the Hubble diagram shows an innate equivocality between the ΛCDM and the tired light model. This means that the strong agreement between the z/µ data, calculated with the parameters of the ΛCDM model, and the experimentally measured z/µ values cannot be considered as definite evidence for the expansion hypothesis. The exponential function , which is characteristic of the tired light redshift mechanism, fits the data with similarly high accuracy. Hence, on the premise of low redshift data, a decision for or against either model is completely arbitrary. The Hubble diagram for high redshift gamma ray bursts shows poor agreement with the ΛCDM model, but concurs with the exponential energy decay following from the tired light redshift hypothesis.
... These supernovae are extremely luminous, with their peak brightness often rivalling that of their host galaxy [91]. Increasingly precise data from SNIa have solidified the original ground-breaking observations and their implications for the expansion of the universe [92][93][94][95][96]. ...
We discuss an interacting decaying vacuum energy and dark matter empowered by gravitationally induced matter creation model, and its impact on structure formation by analysing the growth rate perturbations. Our work is motivated by the possibility that the decaying vacuum is due to quantum field theory and dark matter originates from gravitationally induced matter creation. We delve deeper into our investigation and explore both theoretical and statistical analysis of the cosmological model to test its ability to describe the evolution of the Universe. To achieve this, we use three distinct combinations of datasets from CC, Pantheon SNIa sample, BAO, CMB distance priors and datapoints to constrain the model parameters. Our statistical analysis employs Markov Chain Monte Carlo (MCMC) methods. The deceleration parameter shows that the model transitions from a decelerated phase to an accelerated phase of expansion. The current Hubble parameter values are estimated to be km/s/Mpc, km/s/Mpc, and km/s/Mpc using DS1, DS2 and DS3 datasets, respectively. These values of are very close to those derived from the Planck data. The effective equation of state parameter indicates an accelerating phase, with density parameter for vacuum energy exhibiting expected values. We analyse the stability characteristics through the selection information criteria. We also perform thermodynamic analysis by studying the evolution of entropy in the Universe for the model and find it to be in agreement with the generalized second law of thermodynamics. These findings support that the proposed model effectively describes the evolutionary features of the Universe at both theoretical and observational levels.
... As a reference, constraints for the IDE and RV models obtained in previous studies are summarized in Table 3. For the observational constraints on the IDE model, described by Eq. (54), ̃= 3̃, we reference the results from [31], where a global fit to Planck, BAO, SNIa from Joint Light Analysis (JLA) [76] and 0 data yielded = 0.0007127 +0.000256 −0.000633 at 68% CL. Similarly, [41] analysed using CMB, BAOS, SNIa, and RSD data, obtaining = 0.00088 +0.00088 −0.00068 at 68% CL. ...
... To test the Bianchi 1 -Cartan hypothesis we use the type 1a supernovae Hubble diagram with the Union 2 data sample [10] containing 557 supernovae up to a redshift of 1.4 and the Joint Light curve Analysis (JLA) [11] data sample containing 740 supernovae up to a redshift of 1.3 and 258 common supernovae with Union 2. The celestial coordinates of the Supernovae are obtained from the SIMBAD database [12]. ...
We try to solve the dark matter problem in the fit between theory and the Hubble diagram of supernovae by allowing for torsion via Einstein-Cartan's gravity and for anisotropy via the axial Bianchi I metric. Otherwise we are conservative and admit only the cosmological constant and dust. The failure of our model is quantified by the relative amount of dust in our best fit: Omega_{m0}= 27 % +/- 5 % at 1 sigma level.
... These authors consider only the low-redshift regime in order for their analysis to be model independent. Making use of the two most recent SNe Ia data sets available namely the Union2.1 and the JLA data set [36], Bengaly et al. conclude that they cannot discard the possibility of the existence of a genuine anisotropy in the recent Universe. We point out here that in the present work, in contrast to recent similar studies, we probe the angular power spectrum of SNe Ia at higher redshifts, mainly with the motivation of bulk flow measurement of possibly cosmological origin. ...
We contribute another anisotropy study to this field of research using Type Ia supernovae (SNe Ia). In this work, we utilise the power spectrum calculation method and apply it to both the current SNe Ia data and simulation. Using the Union2.1 data set at all redshifts, we compare the spectrum of the residuals of the observed distance moduli to that expected from an isotropic universe affected by the Union2.1 observational uncertainties at low multipoles. Through this comparison we find a dipolar anisotropy with tension of less that towards and which is mainly induced by anisotropic spatial distribution of the SNe with rather than being a cosmic effect. Furthermore, we find a tension of at between the two spectra. Our simulations are constructed with the characteristics of the upcoming surveys like the Large Synoptic Survey Telescope (LSST), which shall bring us the largest SNe Ia collection to date. We make predictions for the amplitude of a possible dipolar anisotropy that would be detectable by future SNe Ia surveys.
... We use the 740 type Ia supernovae from the Joint Light Curve Analysis (JLA) [1]. The JLA published data provide the observed uncorrected peak magnitude (m peak ), the time stretching of the light-curve (X1) and color (C) at maximum brightness due to intrinsic supernovae property and extinction by dust in the host galaxy. ...
We compute the birefringence of light in curved Robertson-Walker spacetimes and propose an exotic formula for redshift based on the internal structure of the spinning photon. We then use the Hubble diagram of supernovae to test this formula.
... In recent years, the unprecedented quality and quantity of astronomical data has thrown cosmology into the age of precision. The main cosmological parameters have been obtained with errors of a few percent through measurements of the cosmic background radiation (CMB) anisotropies [1,2], observations of type Ia supernovae (SNe Ia) [3,4] and measurements of the clustering of galaxies at different stages of the universe evolution [5,6,7,8] (we refer the reader to [9] for a recent review). ...
The cosmic distance duality relation (CDDR) has been test through several astronomical observations in the last years. This relation establishes a simple equation relating the angular diameter () and luminosity () distances at a redshift z, . However, only very recently this relation has been observationally tested at high redshifts () by using luminosity distances from type Ia supernovae (SNe Ia) and gamma ray bursts (GRBs) plus angular diameter distances from strong gravitational lensing (SGL) observations. The results show that no significant deviation from the CDDR validity has been verified. In this work, we test the potentialities of future luminosity distances from gravitational waves (GWs) sources to impose limit on possible departures of CDDR jointly with current SGL observations. The basic advantage of from GWs is being insensitive to non-conservation of the number of photons. By simulating 600, 900 and 1200 data of GWs using the Einstein Telescope (ET) as reference, we derive limits on function and obtain that the results will be at least competitive with current limits from the SNe Ia + GRBs + SGLs analyses.
... The results of Ref. [4] have been updated by [11], obtaining r d,SBH = 141.1±5.5 Mpc (using JLA type IA SNe data [13], BAO D V /r s measurements [12,14,15] and the Hubble constant H 0 determination of Ref. [16]) and r d,CSB = 150.0 ± 4.7 Mpc when including, instead of H 0 , cosmic chronometer measurements from passive elliptical galaxy ages [17], yielding H(z). ...
We investigate our knowledge of early universe cosmology by exploring how much additional energy density can be placed in different components beyond those in the CDM model. To do this we use a method to separate early- and late-universe information enclosed in observational data, thus markedly reducing the model-dependency of the conclusions. We find that the 95\% credibility regions for extra energy components of the early universe at recombination are: non-accelerating additional fluid density parameter and extra radiation parameterised as extra effective neutrino species when imposing flatness. Our constraints thus show that even when analyzing the data in this largely model-independent way, the possibility of hiding extra energy components beyond CDM in the early universe is seriously constrained by current observations. We also find that the standard ruler, the sound horizon at radiation drag, can be well determined in a way that does not depend on late-time Universe assumptions, but depends strongly on early-time physics and in particular on additional components that behave like radiation. We find that the standard ruler length determined in this way is Mpc if the radiation and neutrino components are standard, but the uncertainty increases by an order of magnitude when non-standard dark radiation components are allowed, to Mpc.
... For our analysis, we updated the CMB data set used in the previous work * , joining the Plik "TT,TE,EE+lowE" CMB Planck (2018) likelihood (by combination of temperature power spectra and cross correlation TE and EE over the range ∈ [30, 2508], the low-temperature Commander likelihood, and the low-SimAll EE likelihood) [34], its lensing reconstruction power spectrum † [34,35] and SNe data from the Joint Light-curve sample [36]. The latter * In Ref. [1] we have used the second release of Planck data [33] "TT+lowP" (2015), namely the high-Planck temperature data (in the range 30 < < 2508) from the 100-, 143-, and 217-GHz half-mission TT cross-spectra, and the low-P data by the joint TT, EE, BB and TE likelihood (in the range 2 < < 29). ...
We investigate the observational viability of a class of interacting dark energy (iDE) models in the light of the latest Cosmic Microwave Background (CMB), type Ia supernovae (SNe) and SH0ES Hubble parameter measurements. Our analysis explores the assumption of a non-zero spatial curvature, the correlation between the interaction parameter and the current expansion rate , and updates the results reported in \cite{micol}. Initially, assuming a spatially flat universe, the results show that the best-fit of our joint analysis clearly favours a positive interaction, i.e., an energy flux from dark matter to dark energy, with , while the non-interacting case, , is ruled out by more than confidence level. On the other hand, considering a non-zero spatial curvature, we find a slight preference for a negative value of the curvature parameter, which seems to relax the correlation between the parameters and , as well as between and the normalization of the matter power spectrum on scales of 8 Mpc (). Finally, we discuss the influence of considering the SH0ES prior on in the joint analyses, and find that such a choice does not change considerably the standard cosmology predictions but has a significant influence on the results of the iDE model.
... Beside an effective equation of state parameter w = −1 (roughly, the value preferred by current observations, e.g. [40][41][42]), we also consider models with w = −0.9 and w = −1.1. In [17] it was found that viability priors do impose tight constraints and well defined patterns for the time scaling of relevant observables of the LSS in the universe. ...
We study the effects of Horndeski models of dark energy on the observables of the large-scale structure in the late time universe. A novel classification into {\it Late dark energy}, {\it Early dark energy} and {\it Early modified gravity} scenarios is proposed, according to whether such models predict deviations from the standard paradigm persistent at early time in the matter domination epoch. We discuss the physical imprints left by each specific class of models on the effective Newton constant , the gravitational slip parameter , the light deflection parameter and the growth function and demonstrate that a convenient way to dress a complete portrait of the viability of the Horndeski accelerating mechanism is via two, redshift-dependent, diagnostics: the and the planes. If future, model-independent, measurements point to either at redshift zero or with at high redshifts or with at high redshifts, Horndeski theories are effectively ruled out. If is measured to be larger than expected in a CDM model at then Early dark energy models are definitely ruled out. On the opposite case, Late dark energy models are rejected by data if , while, if , only Early modifications of gravity provide a viable framework to interpret data.
... Inflation together with Λ cold dark matter leads to the minimal inflationary ΛCDM model. Analyses of the data from CMB [6,7], type Ia supernovae (SNIa) [8] and baryonic acoustic oscillations (BAO) [9] observations allow us not only to fit all free parameters of this model with high accuracy, but also to test its underlying assumptions. The high precision data from WMAP [6] and Planck [7] satellites agree with this model but reveal several unexpected features at large angular scales [10] that might be addressed in the context of anisotropic inflation. ...
We consider the non-minimal model of gravity in -form. We investigate a particular case of the model, for which the higher order derivatives are eliminated but the scalar curvature R is kept to be dynamical via the constraint . The effective fluid obtained can be represented by interacting electromagnetic field and vacuum depending on Y(R), namely, the energy density of the vacuum tracks R while energy density of the conventional electromagnetic field is dynamically scaled with the factor . We give exact solutions for anisotropic inflation by assuming the volume scale factor of the Universe exhibits a power-law expansion. The directional scale factors do not necessarily exhibit power-law expansion, which would give rise to a constant expansion anisotropy, but expand non-trivially and give rise to a non-monotonically evolving expansion anisotropy that eventually converges to a non-zero constant. Relying on this fact, we discuss the anisotropic e-fold during the inflation by considering observed scale invariance in CMB and demanding the Universe to undergo the same amount of e-folds in all directions. We calculate the residual expansion anisotropy at the end of inflation, though as a result of non-monotonic behaviour of expansion anisotropy all the axes of the Universe undergo the same of amount of e-folds by the end of inflation. We also discuss the generation of the modified electromagnetic field during the first few e-folds of the inflation and its persistence against to the vacuum till end of inflation.
... We now believe that our universe is currently undergoing a phase of late-time accelerated expansion through the observations of supernovae [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. To explain this phenomenon, one generally assumes the existence of a substance called dark energy that constitutes roughly 70% of the total energy density of the present day universe. ...
In order to understand the nature of the accelerating expansion of the late-time universe, it is important to experimentally determine whether dark energy is a cosmological constant or dynamical in nature. If dark energy already exists prior to inflation, which is a reasonable assumption, then one expects that a dynamical dark energy would leave some footprint in the anisotropy of the late-time accelerated expansion. To demonstrate the viability of this notion, we invoke the quintessence field with the exponential potential as one of the simplest dynamical dark energy models allowed by observations. We investigate the effects of its quantum fluctuations (the physical origin of the perturbation being isocurvature) generated during inflation and having fully positive correlation with the primordial curvature perturbations, and estimate the anisotropy of the cosmic expansion so induced. We show that the primordial amplitude of quantum fluctuations of quintessence field {\delta\phi}_P can be related to the tensor-to-scalar ratio r, and we calculate the perturbed luminosity distance to first order and the associated luminosity distance power spectrum, which is an estimator of anisotropicity of late-time accelerated expansion. We find that the gravitational potential at large scales and late times is less decayed in QCDM compared to that in {\Lambda}CDM so that the smaller the redshift and multipole, the more relative deficit of power in QCDM. Our results of luminosity distance power spectrum also show the similar conclusions of suppression as that of the previous investigation regarding the effect of quantum fluctuations of quintessence field on the CMB temperature anisotropies.
... • Type Ia supernovae. We use the JLA data for SN Ia provided by the SDSS-II/SNLS3 Joint Light-curve Analysis [128]. ...
Even if the fundamental action of gravity is local, the corresponding quantum effective action, that includes the effect of quantum fluctuations, is a nonlocal object. These nonlocalities are well understood in the ultraviolet regime but much less in the infrared, where they could in principle give rise to important cosmological effects. Here we systematize and extend previous work of our group, in which it is assumed that a mass scale is dynamically generated in the infrared, giving rise to nonlocal terms in the quantum effective action of gravity. We give a detailed discussion of conceptual aspects related to nonlocal gravity and of the cosmological consequences of these models. The requirement of providing a viable cosmological evolution severely restricts the form of the nonlocal terms, and selects a model (the so-called RR model) that corresponds to a dynamical mass generation for the conformal mode. For such a model: (1) there is a FRW background evolution, where the nonlocal term acts as an effective dark energy with a phantom equation of state, providing accelerated expansion without a cosmological constant. (2) Cosmological perturbations are well behaved. (3) Implementing the model in a Boltzmann code and comparing with observations we find that the RR model fits the CMB, BAO, SNe, structure formation data and local measurements at a level statistically equivalent to CDM. (4) Bayesian parameter estimation shows that the value of obtained in the RR model is higher than in CDM, reducing to the tension with the value from local measurements. (5) The RR model provides a prediction for the sum of neutrino masses that falls within the limits set by oscillation and terrestrial experiments. (6) Gravitational waves propagate at the speed of light, complying with the limit from GW170817/GRB 170817A.
... We use the JLA compilation of type Ia supernovae [125] in this work. It is from a joint analysis of type Ia supernova observations. ...
In this paper, we make a deep analysis for the five typical interacting holographic dark energy models with the interaction terms , , , , and , respectively. We obtain observational constraints on these models by using the type Ia supernova data (the Joint Light-curve Analysis sample), the cosmic microwave background data (Planck 2015 distance priors), the baryon acoustic oscillations data, and the direct measurement of the Hubble constant. We find that the values of for all the five models are almost equal (around~699), indicating that the current observational data equally favor these IHDE models. In addition, a comparison with the cases of interaction term involving the Hubble parameter H is also made.
... Other such correlations have since been found e.g. with the host galaxy mass 6 and metallicity 7 . Cosmological parameters are then fitted, along with the parameters determining the light curves, by simple χ 2 minimisation 1, [8][9][10][11] . This method has a number of pitfalls as has been emphasised earlier 12,13 . ...
The "standard" model of cosmology is founded on the basis that the expansion rate of the universe is accelerating at present --- as was inferred originally from the Hubble diagram of Type Ia supernovae. There exists now a much bigger database of supernovae so we can perform rigorous statistical tests to check whether these "standardisable candles" indeed indicate cosmic acceleration. Taking account of the empirical procedure by which corrections are made to their absolute magnitudes to allow for the varying shape of the light curve and extinction by dust, we find, rather surprisingly, that the data are still quite consistent with a constant rate of expansion.
... Type Ia supernovae. We consider the data from the SDSS-II/SNLS3 Joint Lightcurve Analysis (JLA) [90] for SN Ia, using the complete (non-compressed) corresponding likelihoods. Combining the latter with the ones obtained from the Planck data allows one to put an independent constraint on the matter density fraction Ω m , and breaks the CMB degeneracy in the H 0 − Ω m plane. ...
We present a comprehensive and updated comparison with cosmological observations of two non-local modifications of gravity previously introduced by our group, the so called RR and RT models. We implement the background evolution and the cosmological perturbations of the models in a modified Boltzmann code, using CLASS. We then test the non-local models against the {\em Planck} 2015 TT, TE, EE and Cosmic Microwave Background (CMB) lensing data, isotropic and anisotropic Baryonic Acoustic Oscillations (BAO) data, JLA supernovae, measurements and growth rate data, and we perform Bayesian parameter estimation. We then compare the RR, RT and CDM models, using the Savage-Dickey method. We find that the RT model and CDM perform equally well, while the performance of the RR model with respect to CDM depends on whether or not we include a prior on based on local measurements.
... For over a decade, the ΛCDM scenario has been consolidated as the concordance model of cosmology. Since the pioneering works of [1,2], who showed that the cosmological expansion is incompatible with a null Cosmological Constant Λ value at more than 2σ confidence level (CL), this paradigm has been exhaustively tested with larger and more precise SNe catalogues [3,4], Cosmic Microwave Background (CMB) temperature fluctuations [5,6], large-scale structure information [7], as well as ages of old cosmic objects [8,9,10], being the most successful proposal to describe the observations until the present moment. A fundamental cosmological quantity of the concordance model is the Hubble Constant, H 0 , which gives information about the current expansion rate of the Universe. ...
We evaluate the local variance of the Hubble Constant with low-z Type Ia Supernovae (SNe). Our analyses are performed using a hemispherical comparison method in order to test whether taking the bulk flow motion into account can reconcile the measurement of the Hubble Constant from standard candles () with that of the Planck's Cosmic Microwave Background data (). We obtaina Hubble Constant maximal variance of towards the direction. Interestingly, this result agrees with the bulk flow direction estimates found in the literature, as well as previous evaluations of the variance due to the presence of nearby inhomogeneities. We assess the statistical significance of this result with different prescriptions of Monte Carlo simulations, obtaining moderate statistical significance, i.e., 68.7\% confidence level (CL) for such variance. Furthermore, we test the hypothesis of a higher value in the presence of a bulk flow velocity dipole, finding some evidence for this result which, however, cannot be claimed to be significant due to the current large uncertainty in the SNe distance modulus. Then, we conclude that the tension between different determinations can plausibly be caused to the bulk flow motion of the local Universe, even though the current incompleteness of the SNe data set, both in terms of celestial coverage and distance uncertainties, does not allow a high statistical significance for these results or a definitive conclusion about this issue.
... After successfully minimizing the χ 2 function, our analysis yields the estimated values for the model parameters as It is interestingly here to mention that the our derived values of H 0 ≈ 70 and Ω 0m ≈ 0.262 show remarkable consistency with established cosmological constraints. Notably, our H 0 value aligns with [37,38], reporting respectively H 0 = 70.0 ± 2.0 and H 0 = 70.0 ± 2.5 km/s/Mpc. Similarly, our Ω 0m value closely matches [37], where Ω 0m = 0.263 ± 0.022, and [39], Ω 0m = 0.259 ± 0.021. ...
Understanding the accelerating expansion of the universe remains one of the foremost challenges in modern cosmology. This study investigates Barrow Holographic Dark Energy (BHDE), a model inspired by quantum gravitational corrections, within the framework of f(Q,C) gravity. This extension of symmetric teleparallel gravity incorporates the non-metricity scalar Q and the boundary term C, enabling a deeper exploration of cosmic dynamics without relying on a cosmological constant or exotic matter. The BHDE model is analyzed under a flat Friedmann-Robertson-Walker (FRW) metric, focusing on key cosmological parameters such as energy density, isotropic pressure, the equation of state (EoS) parameter, stability conditions and the energy conditions. The results demonstrate that the EoS parameter transitions from matter-like behavior () to negative values at , indicating the dominance of dark energy and its role in the universe's accelerated expansion. As z approaches , the EoS parameter asymptotically converges to , aligning with the CDM model. This work underscores the potential of the BHDE model in f(Q,C) gravity as a comprehensive framework for studying cosmic acceleration. By incorporating Barrow entropy and addressing the interplay between non-metricity and boundary terms, the model provides a dynamic approach to explaining dark energy.
... The Pantheon data sample consists of five subsamples PS1, SDSS, SNLS, low-z, and HST [98]. It has the observational data of 1048 Type Ia supernovae (SN Ia) spanning over the range of z within 0.001 < z < 2.3. ...
Bianchi type III (BIII) metric is an interesting anisotropic model for studying cosmic anisotropy as it has an additional exponential term multiplied to a directional scale factor. Thus, the cosmological parameters obtained for this BIII metric with the conventional energy-momentum tensor within the framework of a modified gravity theory and the estimation of their values with the help of Hubble, Pantheon plus and other observational data may provide some new information in cosmic evolution. In this work, we have studied the BIII metric under the framework of f(R,T) gravity theory and estimated the values of the cosmological parameters for three different models of this gravity theory by using the Bayesian technique. In our study, we found that all the models show consistent results with the current observations but show deviations in the early stage of the Universe. In one model we have found a sharp discontinuity in the matter-dominated phase of the Universe. Hence through this study, we have found that all the f(R,T) gravity models may not be suitable for studying evolutions and early stages of the Universe in the BIII metric even though they show consistent results with the current observations.
... The Pantheon+ sample is made of 1701 light curves from 1550 different SNe Ia ranging z = 0.001 to 2.26, obtained with observations of DES [70,71], Foundation [72], Pan-STARRS [73], Supernova Legacy Survey [74], SDSS [75], HST [62,[76][77][78][79][80] and multiple low-z samples (see [3] for the full list). ...
New constraints on the expansion rate of the Universe seem to favor evolving dark energy in the form of thawing quintessence models, i.e., models for which a canonical, minimally coupled scalar field has, at late times, begun to evolve away from potential energy domination. We scrutinize the evidence for thawing quintessence by exploring what it predicts for the equation of state. We show that, in terms of the usual Chevalier-Polarski-Linder parameters, (, ), thawing quintessence is, in fact, only marginally consistent with a compilation of the current data. Despite this, we embrace the possibility that thawing quintessence is dark energy and find constraints on the microphysics of this scenario. We do so in terms of the effective mass and energy scale of the scalar field potential. We are particularly careful to enforce un-informative, flat priors on these parameters so as to minimize their effect on the final posteriors. While the current data favors a large and negative value of , when we compare these models to the standard CDM model we find that there is scant evidence for thawing quintessence.
... The Pantheon data sample comprised 1048 observational data spanning over the z range between 0.001 < z < 2.3 taken from five subsamples, which include PS1, SDSS, SNLS, low-z and HST [78]. The Pantheon plus sample is the successor of the Pantheon sample and contains 1701 observational data from 18 different sources [79]. ...
The Bumblebee vector model of spontaneous Lorentz symmetry breaking (LSB) in Bianchi type I (BI) Universe to observe its effect on cosmological evolution is an interesting aspect of study in anisotropic cosmology. In this study, we have considered a Bumblebee field under vacuum expectation value condition (VEV) with BI metric and studied the cosmological parameters along with observational data. Further, we have studied the effect of anisotropy and the Bumblebee field in cosmic evolution. We have also studied the effect of both anisotropy and Bumblebee field while considering the Universe as a dynamical system. We have found that there are some prominent roles of both anisotropy and the Bumblebee field in cosmic evolutions. We have also observed an elongated matter-dominated phase as compared to standard cosmology. Moreover, while studying the dynamical system analysis, we have also observed the shift of critical points from standard CDM results showing the anisotropy and the Bumblebee field effect.
... of 740 SNIa gave Ω m = 0.295[Betoule et al., 2014].188 A set of 1048 SNIA, the "Pantheon Sample" combined with Planck 2015189 CMB results gave Ω m = 0.307 ± 0.012[Scolnic et al., 2018, Table 14. ...
Principles of 4/3 differential scaling in Galileo I and Galileo IIIa are applied to cosmology. Cosmological theories and astronomical observations support the validity of Galileo I and Galileo IIIa.
... Plotting the distance moduli for supernovae binned data [Betoule, 2014] gives Figure ...
In the 25 years following the introduction of dark energy to cosmology there has been little progress in understanding this phenomenon. A radical solution is considered-to change the redshift scale-factor relation. The new relation explains why Concordance Cosmology, using the wrong relation, needs a low matter density and dark energy. An alternative cosmology is described that explains how the new relation comes about. There are solutions to the flatness problem, the coincidence problem and the Hubble tension.
... where M is the absolute magnitude of SnIa. We take this model as simplified version of [101,102] with vanishing color-luminosity and stretch-luminosity parameters. ...
We propose a new model of cosmology based on an anisotropic background and a specific f (R) theory of gravity. It is shown that field equations of f (R) gravity in a Bianchi type I background give rise to a modified Friedmann equation. This model contains two important parameters: γ and δ. We, thus, simply call our model γδCDM. It is distinguished in two important aspects from the ΛCDM model: firstly, the contribution of different energy densities to the Hubble parameter are weighted with different weights, and then, dependence of energy densities to redshift is modified as well. This unorthodox relation of energy content to Hubble parameter brings forth a new way of interpreting the cosmological history. This solution does not allow the existence of a cosmological constant component, however, a dark energy contribution with dependence on redshift is possible. We tested observational relevance of the new solution by best fitting to different data sets. We found that our model could accommodate the idea of cosmological coupling of black holes.
... To obtain best-fit values of the cosmological parameters used in the derived model with observational constraints, we have used 518 SNe Ia data of apparent magnitude m(z) from union 2.1 compilation [55], 50 SNe Ia data of m(z) from "Joint Light Curve Analysis (JLA)" as in [56], and 40 SNe Ia Bined data of m(z) from compilation of supernovae pantheon samples in the range 0 ≤ z ≤ 1.7 [57,58]. We have used the following χ 2 test formula to achieve the best-fit curve for theoretical and empirical results: ...
... The first observable that will be considered is the redshift-distance relation which can be obtained observationally from supernovae through their flux magnitude. This magnitude can be directly related to the luminosity distance [71] which can again be related to the angular diameter distance D L through the distance-duality relation, D L = D A (1 + z) 2 [72]. In the FLRW limit, the luminosity distance is given by ...
Phenomenological models are widely used in cosmology in relation to constraining different cosmological models, with two common examples being cosmographic expansions and modeling the equation-of-state parameter of dark energy. This work presents a study of how using different phenomenological expressions for observables and physical quantities versus using physically motivated, derived expressions affects cosmological parameter constraints. The study includes the redshift-distance relation and Hubble parameter as observables, and the dark energy equation-of-state parameter as a physical quantity, and focuses on constraining the cosmological parameter . The observables and equation-of-state parameter are all modeled both using the physical, derived expressions and a variety of phenomenological models with different levels of accuracy and complexity. The results suggest that the complexity of phenomenological expressions only has minor impact on the parameter constraints unless the complexity is very high. The results also indicate that statistically significantly different results can be expected from parameter constraints using different phenomenological models if the models do not have very similar accuracy. This suggests that a good practice is to use multiple phenomenological models when possible, in order to assess the model dependence of results. Straightforward examples of this is that results obtained using cosmographic expansions should always be checked against similar results obtained with expansions of other order, and when using phenomenological models such as for the equation-of-state parameters, robustness of results could be assessed using fitted models from symbolic regression, similar to what is done in this study.
Under the assumption that they are standard(izable) candles, the lightcurves of Type Ia supernovae have been analysed in the framework of the standard Friedmann–Lemaitre–Robertson–Walker cosmology to conclude that the expansion rate of the Universe is accelerating due to dark energy. While the original claims in the late 1990s were made using overlapping samples of less than 100 supernovae in total, catalogues of nearly 2000 supernovae are now available. In light of recent developments such as the cosmic dipole anomaly and the larger-than-expected bulk flow in the local Universe (which does not converge to the Cosmic Rest Frame), we analyse the newer datasets using a Maximum Likelihood Estimator and find that the acceleration of the expansion rate of the Universe is unequivocally anisotropic. The associated debate in the literature highlights the artifices of using supernovae as standardizable candles, while also providing deeper insights into a consistent relativistic view of peculiar motions as departures from the Hubble expansion of the Universe. The effects of our being ‘tilted observers’ embedded in a deep bulk flow may have been mistaken for cosmic acceleration.
This article is part of the discussion meeting issue ‘Challenging the standard cosmological model’.
We consider interacting dark matter-dark energy models arising out of a general interaction term Here f is a functional relation connecting the energy densities and and their derivatives w.r.t. time t. In our model we consider two interacting barotropic fluid with constant equation of state and By considering a dynamical interaction between them we trace out the cosmological evolution dynamics of the universe. We analytically solve the model by considering a constant ratio between the two fluids and then track the corresponding analytical results using observational data from the baryon acoustic oscillation measurements, Type Ia supernovae measurements and the local Hubble constant measurements. From this general setting we introduce three different models and nine different interaction function. Our final aim is to set up a comparative analysis of the various class of models under the different interaction function using common theoretical and numerical analysis.
The questionable notion that the Universe began with a so-called "Big Bang" is at best a tenuous idea. It begs the obvious layperson questions: What was there before it occurred? Where did all the energy and matter come from? What caused it to happen? How will the universe end? On the contrary, in this paper we will provide simple evidence to support the concept of a cyclic universe and estimate the period of each complete cycle. We also postulate that the Universe is, has been, and always will be. It is infinite in space, having no beginning or end. In a metaphysical sense, it is an evolving, ever changing cyclic system that gives birth and swallows up matter in an infinite number of continuous cycles.
Principles of dimensional capacity supply means for a small window of radiation that Thomas Gold conjectures in his 1962 article on the arrow of time.
Galileo showed that magnitudes of a beam's volume and cross-sectional area scale differently due to their different dimensions. But physical dimension is more fundamental than the mathematical scaling it induces. Some twentieth century problems unsolved using scaling --- metabolic scaling and dark energy are examples--- can be solved using dimensions. Revisiting Galileo's 1638 scaling approach helps reveal principles based on dimension missing from physics.
Since 4/3 scaling, which applies to bounded, finite systems, as in metabolic scaling, Peto's paradox and brain weight scaling, also applies to unbounded expanding cosmological space, 4/3 scaling is probably valid and the mathematics of WBE 1997 is probably wrong.
Generalizing Galileo's strength of materials scaling implies 4/3 scaling is a universal physical law, arising in brain weight / body weight scaling, metabolic scaling, Peto's paradox, black body radiation, the fractal envelope of Brownian motion, the expansion of space in cosmology and so on.
ResearchGate has not been able to resolve any references for this publication.